1. Field of the Invention
The present invention relates to an optical information memory medium which is capable of reversibly displaying at least part of information recorded in the optical information memory medium, and also to a display recording method.
2. Discussion of Background
Recently the importance of electronic information memory media for storing, recording and rewriting huge amounts of information is increasing year by year as peripheral devices not only for office use, but also in home use.
Examples of such electronic information memory media include magnetic tape, floppy disk, magneto-optical disk, compact disks(CD) such as CD-DA, CD-ROM, CD-R and CD-RW, DVD-type media such as DVD-ROM, DVD-R and DVD-RAM, integrated circuit (IC) card, optical card, and removal hard disk. Recently memory capacity, and kinds and number of information to be recorded for one medium are significantly increasing. Of these recording media, particular attention is paid to optical information memory media which are capable of storing information and from which recorded information can be read, with the application of laser beams thereto.
As a conventional index recording method for recording the contents, volumes and titles of information recorded in such electronic information memory media and for easily recognizing them visually, a method of applying a self-adhesive index label indicating such information to disk cartridges is employed. More specifically, Japanese Laid-Open Patent Application No. 9-282836 proposes a liquid crystal/polymer composite film to be used as such an index label, which is capable of rewriting displayed information.
However, in the case of compact disks, no cartridges are used, but the media are used alone, so that there is a problem that if the above-mentioned liquid crystal/polymer composite film is provided on the surface of the disk, the disk becomes too thick as a whole to be used in rotation for reading recorded information or for writing information therein by the application of laser beams thereto.
In the case of CD-ROMs, some data is already recorded therein when produced so that CD-ROMs are used exclusively for reproduction. In such CD-ROMs, index displays indicating the contents of recorded information and various designs are printed on the surface of a protective layer therefor, using an ultraviolet-curing ink or an oil ink. Such printing is usually carried out by screen printing or offset printing, which is suitable for performing multiple printing for printing a number of the same patterns at the same.
Write-once type optical information memory media (CD-R), which are capable of recording information once therein and reproducing the recorded information using a CD player, have now been developed, so that end-users themselves may record their own information such as music or computer data in the CD-R. The CD-R does not bear anything on the surface thereof or merely bears only printed general characters or patterns, using an ultraviolet-curing ink or an oil ink, so that the user may write his or her notes regarding recorded personal information on the surface of a protective layer for the CD-R, using a felt pen, or apply an index display label indicating his or her notes to the surface of the protective layer, or perform display recording by an ink jet printing method on an ink-receiving layer provided on the CD-R as proposed in Japanese Laid-Open Patent Application No-5-238005, or perform display recording by a sublimation type thermal image transfer recording method on a dye-receiving layer provided on the CD-R as proposed in Japanese Laid-Open Patent Application No. 8-48080.
Furthermore, rewritable optical information memory media (CD-RW) in which recorded information can be rewritten by the application of laser beams thereto have now been developed. In the case of the CD-RW, however, once the user write his or her notes regarding recorded personal information on the surface of the protective layer for the CD-RW, using a felt pen, or applies an index display label indicating his or her notes to the surface of the protective layer, for instance, using a thermal image transfer recording method, even if the recorded information is rewritten, it is not always easy to rewrite the notes or change the index display label, without damaging the CD-RW.
It is therefore a first object of the present invention to provide an optical information memory medium free of the above-mentioned shortcomings of the conventional optical information memory media, provided with a reversible display function of making it possible to make visual confirmation of the contents of information recorded in the medium by displaying the same, and also to record, erase and rewrite the display easily and neatly without making any damage to the optical information memory medium.
A second object of the present invention is to provide a display recording method, using the above-mentioned optical information memory medium.
The first object of the present invention can be achieved an optical information memory medium, comprising, in the stated order:
(a) a substrate,
(b) an optical information memory layer which is capable of memorizing information therein, and
(c) a reversible display recording layer which is capable of rewritably recording therein, in a visibly recognizable form, at least part of an information corresponding to said information memorized in the optical information memory layer.
In the above-mentioned optical information memory medium, the reversible display recording layer may be a reversible thermosensitive display recording layer of which transparency or color tone thereof is thermally reversibly changeable.
In the above optical information memory medium, the substrate may comprise a resin having a glass transition temperature Tg(xc2x0 C.), and the reversible thermosensitive display recording layer may have a recording temperature Tr(xc2x0 C.), with the glass transition temperature Tg(xc2x0 C.) and the recording temperature Tr(xc2x0 C.) being a relationship of:
Trxe2x89xa61.6xc3x97Tgxe2x80x83xe2x80x83(1) 
Furthermore, in the above optical information memory medium, the substrate may comprise a resin having a glass transition temperature Tg(xc2x0 C.), and the reversible thermosensitive display recording layer may have a recording temperature Tr (xc2x0 C.) and a thickness Lr (xcexcm), and the distance between (a) a surface of the substrate on the side of the reversible thermosensitive display recording layer and (b) a surface of the reversible thermosensitive display recording layer on the side of the substrate is Ld (xcexcm), with the glass transition temperature(xc2x0 C.) of the resin, the recording temperature Tr(xc2x0 C.) and the thickness Lr(xcexcm) of the reversible thermosensitive display recording layer, and the distance Ld (xcexcm) being a relationship of:                     Tr        ≤                  1.3          xc3x97          Tg          xc3x97                                    Lr              +              Ld                                      Lr              +                              0.8                xc3x97                Ld                                                                        (        2        )            
In the above optical information memory medium, the recording temperature Tr of the reversible thermosensitive display recording layer may be 120xc2x0 C. or more.
In the optical information memory medium, the reversible thermosensitive display layer may comprise a matrix resin and an organic low-molecular-weight material dispersed in the matrix resin, and may have a transparency which is reversibly changeable with the application of heat thereto.
In the above optical information memory medium, the organic low-molecular-weight material may comprise as at least part of the organic low-molecular-weight material an organic low-molecular-weight component with a melting point of 100xc2x0 C. or more, but not more than 1.6 times the glass transition temperature of the resin of the substrate.
In the above optical information memory medium, the organic low-molecular-weight material may also comprise at least two organic low-molecular-weight components with different melting points with a difference of at least 30xc2x0 C.
In the optical information memory medium of the present invention, the reversible thermosensitive display recording layer may comprise an electron-donating coloring material and an electron-accepting material capable of inducing color formation in the electron-donating coloring material by a coloring reaction between the electron-donating coloring material and the electron-accepting material, and the electron-accepting material may comprise at least as part of the electron-accepting material an electron-accepting compound with a melting point of 120xc2x0 C. or more, but not more than 1.6 times the glass transition temperature of the resin of the substrate.
In the above-mentioned optical information memory media of the present invention, the resin of the substrate may have a glass transition temperature Tg of 100xc2x0 C. or more.
Furthermore, in the above-mentioned optical information memory media of the present invention, the resin of the substrate may have a glass transition temperature Tg of 180xc2x0 C. or less.
It is preferable that the optical information memory media of the present invention have a warping angle of xc2x10.6 deg or less and a warpage of 0.4 mm or less.
The optical information memory media of the present invention may further comprise a support for supporting thereon the reversible display recording layer and an adhesive layer or a tacky layer provided on a back side of the support opposite to the reversible display recording layer for fixing the reversible display recording layer supported on the support to the optical information memory layer, thus the adhesive layer or the tacky layer, the support and the reversible display recording layer constituting a reversible display recording label, so that the reversible display recording label can be applied to the optical information memory layer through the adhesive layer or the tacky layer.
In the above optical information memory media of the present invention, the information recorded in the reversible display recording layer in the visibly recognizable form may be in the form of a bar code.
Furthermore, the optical information memory media of the present invention may further comprise a light reflection layer for improving a display contrast of the reversible display recording layer which is provided behind the reversible display recording layer.
The optical information memory media of the present invention may further comprise a light reflection and heat dissipation layer for reflecting laser beams thereby and preventing the optical information memory layer from being heated, which light reflection and heat dissipation layer is provided between the optical information memory layer and the reversible display recording layer, nearer the optical information memory layer.
In the above optical information memory media of the present invention, the light reflection and heat dissipation layer can also serve as a light reflection layer for improving a display contrast of the reversible display recording layer, which is provided behind the reversible display recording layer.
In the optical information memory media of the present invention, it is preferable that a top surface of the optical information memory media on the side of the reversible display recording layer have a Ten-Point Mean Roughness (Rz) in a range of 0.3 to 3.0 xcexcm (JIS B0601).
In the optical information memory media of the present invention, it is also preferable that a top surface of the optical information memory media on the side of the reversible display recording layer have a Center-line Mean Roughness (Ra) in a range of 0.05 to 1.0 xcexcm (JIS B0601).
The optical information memory media of the present invention may further comprise a reversible display recording area on part of a surface of the substrate on the side of the optical information memory layer, and also an irreversible display recording area on the same surface as that of the surface of the substrate.
In the above optical information memory media of the present invention, the irreversible display recording area may be a hydrophilic surface to which a water base ink can be fixed.
Alternatively, in the above optical information memory media of the present invention, the irreversible display recording area may comprise an image receiving layer to which images formed by a thermal image transfer recording method can be fixed.
The second object of the present invention can be achieved by a display recording method, using any of the above-mentioned optical information memory media of the present invention, comprising the steps of:
memorizing and/or rewriting information that can be optically read by applying a laser beam thereto in the optical information memory layer, and
recording and/or rewriting at least part of the memorized and/or recorded information in the reversible display recording layer in a visibly recognizable form.
In the above display recording method of the present invention, the reversible display recording layer may be a reversible thermosensitive display recording layer with a transparency or a color tone thereof being thermally changeable, and at least part of the information memorized and/or recorded information in the optical information memory layer can be recorded and/or rewritten in the reversible thermosensitive display recording layer with the application of heat thereto in the visibly recognizable form.
In the above display recording method, at least part of the information memorized and/or recorded information in the optical information memory layer can be recorded and/or rewritten in the reversible thermosensitive display recording layer, with the application of heat thereto at a temperature which is 1.6 times or less a glass transition temperature of the resin of the substrate, in the visibly recognizable form.
Furthermore, in the above display recording method of the present invention, at least part of the information memorized and/or recorded information in the optical information memory layer can be recorded and/or rewritten in the reversible thermosensitive display recording layer in the visibly recognizable form, with the application of heat thereto at a temperature corresponding to at least a temperature obtained by multiplying a glass transition temperature of the resin of the substrate by the following:       1.3    xc3x97          (              Lr        +        Ld            )            Lr    +          0.8      xc3x97      Ld      
wherein Lr is the thickness (xcexcm) of the reversible thermosensitive display recording layer, and Ld is a distance (xcexcm) between (a) a surface of the substrate on the side of the reversible thermosensitive display recording layer and (b) a surface of the reversible thermosensitive display recording layer on the side of the substrate.
Furthermore, the optical information memory medium for use in the display recording method may further comprise a reversible display recording area on part of a surface of the substrate on the side of the optical information memory layer, and also an irreversible display recording area on the same surface as that of the surface of the substrate. In this case, the above display recording method of the present invention further comprises a step of depositing imagewise a material comprising a dye or a pigment on the irreversible display recording area.
In the above optical information memory medium, the irreversible display recording area may be a hydrophilic surface. In this case, as the material comprising a dye or a pigment, a water base ink may be used and may be deposited imagewise on the irreversible display recording area by an ink jet printing method to form an image thereon.
In the above optical information memory medium, the water base ink may be deposited imagewise on the irreversible display recording area by an ink jet printing method to form an image thereon.
The material comprising a dye or a pigment can also be deposited imagewise on the irreversible display recording area by a thermal image transfer method.